The by-products are dimethyl sulfide ((CH3)2S), carbon monoxide (CO), carbon dioxide (CO2) and—when triethylamine is used as base—triethylammonium chloride (Et3NHCl). Of the volatile by-products, dimethyl sulfide has a strong, pervasive odour and carbon monoxide is acutely toxic, so the reaction and the work-up needs to be performed in a fume hood. Dimethyl sulfide is a volatile liquid (B.P. 37 °C) with an unpleasant odour at even low concentrations.[8][9][10]
^Mancuso, A. J.; Brownfain, D. S.; Swern, D. (1979). "Structure of the dimethyl sulfoxide-oxalyl chloride reaction product. Oxidation of heteroaromatic and diverse alcohols to carbonyl compounds". J. Org. Chem.44 (23): 4148–4150. doi:10.1021/jo01337a028.{{cite journal}}: CS1 maint: multiple names: authors list (link)
^Mancuso, A. J.; Huang, S.-L.; Swern, D. (1978). "Oxidation of long-chain and related alcohols to carbonyls by dimethyl sulfoxide "activated" by oxalyl chloride". J. Org. Chem.43 (12): 2480–2482. doi:10.1021/jo00406a041.{{cite journal}}: CS1 maint: multiple names: authors list (link)
^Tidwell, T. T. (1990). "Oxidation of alcohols to carbonyl compounds via alkoxysulfonium ylides: The Moffatt, Swern, and related oxidations". Org. React. (Review). 39: 297–572. doi:10.1002/0471264180.or039.03. ISBN0471264180.
^Tidwell, T. T. (1990). "Oxidation of alcohols by activated dimethyl sulfoxide and related reactions: An update". Synthesis (Review). 1990 (10): 857–870. doi:10.1055/s-1990-27036.